Electric generating system.



H. H. WAIT.

ELECTRIC GENERATING SYSTEM.

urmcnxon rum) 0017,1909.

1,078,1 79. Patented Nov. 11, 1913.

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" speed dynamos of Improvement in UNITED snares HENRY ELECTRIC GENERATING SYS'I'EI Specification of Letters i liifjf r OFFICE. a,

Application filed October 7. 1909. Serial No. 521.;48.

To all whom itmay concern.

Be it known that I. l'lENltY H. V Arr, citizen of the United States, residing at Chicago,in the county of Cook and State of l llin'ois, have invented a certain new anduseful Electric Generating Systems, of which the following is a full, clear, concise, and exact description.

My invention relates to an electric. generating system and particularly to high speed direct current generating sets in which two dynamos are mechanically connected together and operated from a single prime mover such as a'stcam turbine.

" It is frequently fonud desirable to connect. two or more (lynamcs otherprime mover for the reason that two smaller generators can be run at a higher number of revolutions than if the generator consisted of single large unit. In high this character, itis usually ne'cessary, on account of the high speed of commutation,- to provide some. special means of accomplishing the sparkless commutation of the current. As it is wel known, compensating windings ployed for such purposes these windings producing a magnetizing effect at an "angle of approximately 90, electrically considered, from that of the main magnetizing windings.

always more or Dynamos of this character are less sensitive to changes in load or conditions, because the high speed of the machines naturally results in a character of design in which the armature and the series windings on the field have a small number of turns of large cross section as compared with a slow speed machine of the some rating. The high speed makes it necessary also to use low magnetic densities in the armature-to avoid excessive heating. There is consequently neither the ordinary internal resistance of the machine nor the magnetic saturation of the armature to ro'i'ide the requisite inherent tendency to stability of load. On the other hand, the peripheral speed of the commutators' of such machines is generally very high and the resistance ol-the brush contactis a very large proportion of the total resistance to t e current in passing through the machine. This contact resistance, on account of the high speed and consequently low permissible brush tension, is very sensitive to such differences in resistance as are produced by lubrication or dirt on the commutator, so

to the'same turbine or of the machine that. there a tendency to pro lucevi0lent shifting of the load from one machine to another which is operating in parallel with it by very small disturbing causes. j

It is not possible to connect an equalizing wire or nus directly between the terminals of the arniaturcs as is the usual practice, in ordinary dynanios, because this would distribute the current in the compensating '5 windings-Yin proportion to the external ,resistanrcs their circuits, whereas the cur-z" rent in the. compensating windings should be proportional in each to its oivn armature current.

If the main series windings were connected on each machine in the usual way with an equalizing connection, therewoul he difiiculty from the violent shifting offload from one machine to"the other. This isbecause the machines are both rigidly connected to the same prime mover, so that'the machine taking the greater load cannot slow down and give up part of itsload to'the other, as would be the case ifthey"\vere-"g0 connected to separate engines as in ordinary practice n such machines, although the compensating windings act, approximately at right, angles to the main magnetizing effect, and are therefore mainly ueutraliin' gs effect. on .the voltage, their strength and direction of force are sometimes such asl'to add a magnetizing component, which will tend to increase the voltage on load. In any event, they approximately neutralize" the '90 cross magnetizing effect of the armature which, in ordinary machines, tends to distort the field flux and thereby to introduce stability with increasing load. It will therefore be seen that such machines would havea tendency to be unstable when connected together by an equalizer, either at the armature terminals or between the main series windings. This difiiculty of instabilityfit has been the object of my invention to overwe come.

My invent-ion contemplates an arrangement for producing stability in the system and dividing the load approximatelv between the ditferent generators of a set driven by a common prime mover.

The invention consists in roviding in addition to the shunt field winding and compensating series winding a compound series winding so connected in the system that as 11 the load increases on one machine the field strength of the ther machine is increa thereby decreasing and vice versa. The preferredspcific embodiment of my invention consists in connecting the compound series field of each of two machines in series with the armature and compensating series windings of the other machine.

The several features of my invention may be more readily understood by reference to the accompanying drawing showing diagrammatically a, generating set embodying my invention.

T indicates a steam turbine or other high speed prime mover and A, and A indicate the armatures of two direct current generators, su'ch armatures being mechanically connected together and driven either directly or in other suitable manner from the prime mover T.

S, S and C, C are the usual shunt field and the series compensating windings, respectivel B an B are the compounding series windings of the generators A and A, respectively. It will be particularly noted t at by means of cross connections b and b, respectively, the compounding series windings of onemachineare connected in series with the compensating winding and the armature of the other machine. By-such an arrangement if there should be such an increase in resistance at the brushes or elsewhere on one machine as would tend to decrease the load on that machine the current in the series compounding winding on the other machine will likewise be decreased, the compounding eifect on the other machine, so that there is a tendency to divide the load equally between the two machines in spite of such causes as may tend to produce a fluctuation in the load of either machine.

'Anordinary compound dynamo A having the shunt and series windings a and B respectively, may be employed in parallel with the turbine set A and A for supplying current to i the mains. Since the series coils B of such machine A are ordinarily of higher resistance than the series bodiriient of my invention,

1. In an electric generatingv system, the.

coils of the turbo-generators A and A, there is a tendency, when the equalizer connection E is closed, for too much current to go through the turbogenerator orgenerators connected to the generator A by said equalizer connection. Rheostats K and K are hence provided by means of which the cur rent flowing through the coils B and B can be adjuste The switch F connected to the equalizer E permits of connecting the generator A with either of the generators A or A or of disconnecting 't'from both of said generators A and A. Witches J and J are also preferably provided for shortcircuiting portions of the series windings B and B and thereb adjusting the compounding efiect of t e dynamo-so as to get thebest operation whether or not the turboset A, A is running in parallel with the enerator A Having thus described the preferred emwhat I claim is:

combination with a prime mover, of two generators mechanically connected together and electrically connected to the same load, each of said generators being provided with a compensating series winding and a compounding series winding, said latter winding of each machine being electrically connected in series with the other machine.

2. In an electric generating system, the combination with a plurality of generators connected in parallel, each generator being provided wit series compensating windings and series compounding windings, sai compensating windings of each machine being connected in series with its own armature, and said compoundim windings of each machine being connecte in series with the armature of another of said generators.

In witness whereof, I hereunto subscribe my name this fifth day of October, A. D. 1909.

Witnesses:

GEORGE E. Fonn, McCLeLnAno Younc.

HENRY H. WAIT: 

